Conversion of hydrocarbons



April 23, 1940. L. c. RUBIN CONVERSION OF HYDROCARBONS Filed June 1, 1939 INVENTOR 4 (00/3 C/P/fi/IV ATTORNEY Patented Apr. 23, 1940 UNITED STATE CONVERSION OF HYDROGARBONS Louis 0. Dublin, West Caldwell, N. J., assignor to The Polymerization Process Corporation, Jersey City, N. J., a corporation of Delaware Application June 1, 1939, Serial No. 278,835

4 Claims.

This invention relates to the polymerization of olefins to higher boiling hydrocarbons. More particularly, the invention relates to the conversion of normally. gaseous olefins, particularly propylenes and butylenes, to polymers within the gasoline boiling range. Still more particularly, the

invention relates to a process for the treatment of such gaseous olefins by contact thereof at ele- 1 vated conditions of temperature and pressure with a catalyst comprising as an essential ingredient a metal pyrophosphate.

Certain pyrophosphates including those of copper, zinc, magnesium, iron, aluminum and cobalt are capable of promoting the polymerization of olefins but it has been found necessary to pass the hydrocarbons under treatment over the catalytic material containing the pyrophosphate for some time 'at elevated temperature in order to initiate the conversion of olefins to polymer products. Apparently the pyrophosphate is ac- .tivated by the production therein of a modification containing the active centers for accelerating polymerization of olefins.

flcation of the pyrophosphate probably is formed 8' by reduction such as reduction of the copper of copper pyrophosphate from the cupric to the cuprous state to form acid cuprous pyrophosphate. The length of time and the temperature necessary for this activation period depends somewhat upon the method by which the pyrophosphate is produced. 1!, in the production of certain metal pyrophosphates by reaction of a soluble phosphate such as sodium pyrophosphate and a soluble metal salt anexcess of the pyrophosphate is employed it is found that the resulting product is stabilized against reduction to the active modification. Probably this results from the formation of a double salt of sodium pyrophosphate and the metal pyrophosphate action at a temperature of 350 F. while it may he necessary .to passthe hydrocarbon mixture '1 und er treatment over h the; catalytic mass at a higher temperature in order to initiate the conersion of olefins. Whencopper pyrophosphate cntaet agent is prepared utilizing sodium pyrohosphate in an amount'which is 10 percent in aces; "of the amount-equivalent 't o' 'copper sulate accordingto the reaction 2eusoi+nampicu raoa+2m=so4 e presence of the doublesalt which is contained The active modiwhich acts as a reduction inhibitor. Under these the activation period which may nrthe resulting product necessitates passing the illisoleflnic mixture under treatment over the contact agent for a period of as muchas fifty hours while raising the temperature to 500 F. in order to initiate conversion of the olefins to polymer products. Thereafter the desired lower operating temperature may be employed.

It is believed that during the active life of a contact agent reduction is continuous with the gradual production of the active material. The reduction products formed originally appear to act as nuclei, which promote the reduction of additional material. For example, the reduction products formed at the high activating temperature mentioned above act to promote the reduction of additional material at the lower operating temperature since it is found that no loss of conversion rate results from reduction of the temperature from the high activating temperature to the lower polymerizing temperature.

If an excess of the sodium pyrophosphate is" avoided in the preparation 01 the catalytic material whereby it does not contain the double salt, it is found that the activation periodnecessary is shortened, and it may not be necessary to raise the temperature during the activation period substantially above the desired polymeriza- '25 tion reaction temperature. However, it may be desirable to form the double salt in the copper pyrophcsphate when the latter is to be used under certain conditions of operation since, in its absence, the catalytic material may under'some circumstances reduce more rapidly to the active modification than required for the continuance of the polymerizing reaction at a steady rate. Under these conditions the contact agent soon loses its mechanical form and exhibits a relatively short active life. As an example of the use of catalytic material containing the stabilized, or reduction inhibitor, it may be desired to operate of low olefin content or one containing refractory olefins such as ethylene. Under these conditions a highly desirable since the reduction conditions are quite severe and might otherwise cause the material to become reduced too rapidly for continuance of the polymerizing reaction at a steady rate.

The initiation of the polymerizing activity of the metal pyrophosphate by the passage thereover of the olefinic gas under treatment results in undesirable waste of gases containing substantialproportions of convertible constituentsdur- .ing the activation period. Furthermore, the employment of temperatures higher than the reacat high temperatures on a gaseous feed,

stabilized catalytic material is -tion temperature during the activation period, it

necessary, requires periodically raising-{the temperature to which the reaction gases are heated above the temperature to which they are normally heated for the polymerization reaction. This necessitates the provision of heating capacity for the reaction gases in excess of that through reactor 6 is controlled to maintain the gases in contact with the "catalytic body for a time sufiicient to effect the desired polymerization of the olefins. If the' hydrocarbon gas contains a substantial proportion of isobutylene, and if it is desired to effect selective polymerization of the isobutylene the time of contact of hydrocarbon gas on the catalytic material is limited to effect polymerization of isobutylene and any desired proportion of the normal olefins present. In any case the olefin content of the hydrocarbon gas will be reduced sharply by the polymerization treatment in reactor 6. For example, a hydrocarbon gas having an olefin content of 50 per cent by weight may have the olefin content thereof reduced to approximately 10 per cent by polymerization of the remaining olefin content to liquid products.

The mixture of polymers and unreacted gases passes from reactor 6 into header l0. Valve 23 in header I0 is open while valve 24 is closed whereby the mixture of polymers and gases flows from header l0 into line H by which the mixture is transferred to fractionator I2.

In fractionator l2 the mixture of polymers and unreacted gases is fractionated to separate the mixture into a liquid fraction containing the polymers and a gaseous fraction containing the unconverted gases which are undesired in the liquid product. The liquid product is withdrawn through line l3, and the gases are withdrawn through line H.

After the activity of the catalytic material in reactor 6 has been lowered substantially, for example, by the deposition of carbonaceous materials on the active centers of the catalyst the how of the hydrocarbon gas from line I may be transferred to reactor 1. This is effected by opening valves 9 and 24 and closing valves 8 and 23. Thereafter the polymerization treatment continues in the manner described above with the substitution of reactor l in place of reactor 6, re-

actor I being provided with-a granular catalytic mass similar to that of the reactor 6.

During the period in which the gases flow through reactor lthe activity of the reactor 6 is restored by replacing the catalytic material contained therein.

After such replacement alytic material with fresh material mass contained in reactor 6 is subjected to treatof the deactivated catment in accordance with the present invention to v initiate the polymerizing activity of the catalytic material. For this purpose a portion or all of the gases withdrawn from fractionator l2 through line H are diverted through line [5, valves l6 and I! being provided to effect the diversion of the desired proportion of the gases. These gases, which contain a reduced proportion of olefins, are preheated to elevated temperature, for example, 300 to 600 F. by passage through a heater l8 or other suitable heat exchange means. From heater I8 the preheated low olefin gases are withdrawn through line H) which connects with a header 2Uwhich in turn connects with header 5 at a point between valve 8 and reactor 6 and at a point between valve 9 and reactor I. With reactor 1 in use the low olefin gases from line l9 are directed to header 5 at the point between valve 8 and reactor 6 by having valve 22 closed and valve 2| open. The low olefin gases thereby are passed through reactor 6 at elevated temperature in order to bring the body of catalytic material to the desired temper ature for the polymerizing reaction and also to the catalytic effect the initiation of the polymerizing activity of the metal pyrophosphate by reduction thereof to the active modification. After passage of the low olefin gases through reactor 6 they are withdrawn through header Ill and diverted therefrom through header 25 and line 28, valves 23 and 21 being closed.

The pressure maintained during the passage of the low olefin gases through reactor 6 may be that of fractionator l2 or lower, or the pressure in reactorv B may be maintained higher than that of fractionator 12 by the inclusion of a compressor in line l5.

' .Under some circumstances it may be desirable to pass the products from reactor 6 during the activation treatment thereof to fractionator 12 along with the products of reaction from reactor 1 which is on stream. Under these circumstances header 25 would not be used, and valve 23 would be open. Pressure means, such as a compressor in line l5, would be provided to effect the desired recirculation of the low olefin gases. This operation may be employed when it is desired to recover in fractionator l2 the small amount of polymer products which are formed in the low olefin content gas during the activation treatment.

The invention has been described with reference to relatively simple apparatus for purposes of illustration. It will be understood, however, that the process in commercial'application thereof ordinarily will employ more than two reactors. In fact for smooth operation of the process it is desirable to employ a sufficient number of reactors so that a plurality of reactors will undergo replacement of catalytic material and activation. By this method of operation at least one reactor is in the process of activation at all times so that there is a continuous diversion of a portion of the low olefin content gases from line It for use as an activating medium. Under this method of operation there will be produced con-' tinuously from a reactor undergoing activation treatment a stream of gases of low olefin content and containing a small proportion of polymer products. Such material may be returned to the fractionator for recovery of the polymer products or may be diverted from the system for further treatment elsewhere for recovery of the polymer products.

It is thus seen that the present invention itiating passage of said olefinic gas through a catalytic mass containing a metal pyrophosphate as the essential ingredient and which had not been treated previously to initiate the polymerizing activity of the pyrophosphate.

I claim: l

1. A process for treating a hydrocarbon mixture relatively rich in olefins to effect polymerization of said olefins which comprises passing said hydrocarbon mixture over a' catalytic mass containing a metal pyrophosphate which has been ,reduced at least in part to a modification containing active centers for accelerating polymerizatio'nof olefins, contact of said hydrocarbon mixture and said catalytic mass being brought about under-conditions of temperature, pressure and-" time efiective to produce substantial poly- 'inerization of said olefins to higher boiling products, separating from the products of said polymerization reaction a relatively high-boilingpolymer product and a relatively low-boiling hydrocarbon mixture containing unpolymerized constituents of said reaction products and having an olefin content which is appreciable but substantially lower than that of said first-mentioned hydrocarbon mixture, passing said lastification and initiate polymerization of oleflns,

then discontinuing passage of said hydrocarbon mixture of reduced olefin content over said second catalytic mass and initiating passage thereover of a hydrocarbon mixture relatively rich in olefins under the said polymerizing conditions of temperature, pressure and time.

2. A process in accordance with claim 1 wherein said hydrocarbon mixture of low olefin content has an olefin content of at least 10 per cent by weight.

3. A process in accordance with claim 1 wherein said hydrocarbon mixture undergoing treatment consists essentially of C: and C4 hydrocarbons including C3 and C4 olefins.

4. A process in accordance with claim 1 -wherein contact of said hydrocarbon mixture of low olefin content with said catalytic mass which is not reduced to the active modification is eifected at a temperature substantially higher than that of said polymerizing treatment.

LOUIS C. RUBIN. 

